NXP MSC8126 Reference guide

SC100 Application Binary Interface

MNSC100ABI/D

Rev. 2.0, 06/2002

SC100 Application Binary Interface

MNSC100ABI/D

Rev. 2.0, 06/2002

This document contains information on a new product. Specifications and information herein are subject to change

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SC100 Application Binary Interface iii

Chapter 1

Introduction

1.1 Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-1

1.2 Conformance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-2

1.3 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-2

1.4 Revision History. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-3

1.5 Acknowledgements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-4

Chapter 2

Low-Level Binary Interface

2.1 Core Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-1

2.2 Endian Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-2

2.3 Fundamental Data Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-2

2.4 Aggregates and Unions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-6

2.5 Bit Fields. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-8

2.6 Function Calling Sequence. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-10

2.6.1 Argument Passing and Return Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-10

2.6.2 Variable Argument Lists. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-12

2.6.3 Stack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-12

2.6.4 Stack Frame Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-13

2.6.5 Stack Unwinding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-14

2.6.6 Register Saving and Restoring Functions. . . . . . . . . . . . . . . . . . . . . . . . . . . .2-16

2.6.7 setjmp and longjmp Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-17

2.6.8 Frame and Global Pointers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-17

2.6.9 Dynamic Memory Allocation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-17

2.6.10 Hardware Loops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-17

2.7 Function Call Modes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-18

2.8 Address Modifier Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-18

2.9 Saturation Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-18

2.10 Data Addressing Models. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-18

Chapter 3

High-Level Languages Issues

3.1 C Preprocessor Predefines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-1

3.2 C Name Mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-1

3.3 C System Calls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-2

3.4 Fractional Arithmetic Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-2

Table of Contents

iv SC100 Application Binary Interface

3.5 Libraries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-4

3.5.1 Compiler Assist Libraries. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-4

3.5.2 Floating-Point Routines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-4

3.5.3 Integer Routines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-10

3.5.4 Optional Integer Routines. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-11

3.6 Function Argument and Return Type Checking in C. . . . . . . . . . . . . . . . . . . . . .3-12

3.6.1 Signature Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-12

3.6.2 Return Value. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-13

3.6.3 Using Signature Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-13

3.7 Access to Architectural Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-14

Chapter 4

Object File Format

4.1 Interface Descriptions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-1

4.2 The ELF Header . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-2

4.3 Sections. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-3

4.4 Special Sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-5

4.5 Relocation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-6

4.5.1 Relocation Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-7

4.5.2 Relocation Stack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-17

4.5.3 Instruction Address vs. VLES Address . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-18

4.6 NOTE Section. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-19

4.7 Program Headers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-21

4.8 Debugging Information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-22

4.8.1 DWARF Register Number Mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-22

Chapter 5

Assembler Syntax and Directives

5.1 Assembler Significant Characters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-1

5.2 Assembler Directives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-2

5.3 Assembler Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-3

5.3.1 Symbol Names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-3

5.3.2 Strings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-3

5.3.3 Source Statement Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-4

5.3.3.1 Instruction Groups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-5

5.3.3.2 Labels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-5

5.3.3.3 Operation Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-5

5.3.3.4 Operand Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-6

5.3.3.5 Comment Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-6

5.4 Rule Checking. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-6

SC100 Application Binary Interface v

2-1 Mapping of C Data Types to SC100. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4

2-2 Mapping of C Fractional Types to SC100 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5

2-3 C Bit Field Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-8

2-4 Register Usage in the Calling Convention . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-11

3-1 Predefined Macros . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

3-2 Required Intrinsics for Fractional Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2

3-3 Floating-Point Routines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5

3-4 Integer Routines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-10

3-5 Optional Integer Routines. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-11

3-6 Italicized Fields in the Symbol Names. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-12

3-7 Basetype Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-13

3-8 Intrinsics for Access to Architectural Features. . . . . . . . . . . . . . . . . . . . . . . . . 3-14

4-1 SC100 ELF Sections. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4

4-2 Relocation Type Definitions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8

4-3 Relocation Stack Operations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-17

4-4 SC100 Register Number Mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-22

5-1 Assembler Significant Characters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

5-2 Assembler Directives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2

List of Tables

vi SC100 Application Binary Interface

SC100 Application Binary Interface vii

2-1 Stack Frame Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-13

4-1 Object File Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

4-2 Vendor Identification Note Format. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-20

4-3 User (Application-Specific) Note Format. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-20

5-1 Basic Source Statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4

List of Figures

viii SC100 Application Binary Interface

SC100 Application Binary Interface ix

2-1 Word Bit and Byte Numbering. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2

2-2 Long Word Bit and Byte Numbering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3

2-3 Double-Long Word Bit and Byte Numbering . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3

2-4 Structure With Internal and Tail Padding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6

2-5 union Allocation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7

2-6 Bit Field Alignment and Padding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-9

2-7 Unnamed and Zero-Width Bit Fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-9

2-8 Function Calls and Allocation of Arguments. . . . . . . . . . . . . . . . . . . . . . . . . . 2-11

2-9 Generating Stack Unwinding Symbols in Assembly Code . . . . . . . . . . . . . . . 2-15

2-10 Saving and Restoring Functions Usage Example. . . . . . . . . . . . . . . . . . . . . . . 2-16

2-11 Memory Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-19

2-12 Small and Tiny Memory Mode Instruction . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-19

4-1 ELF Header Structure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2

4-2 SC100 Specifics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2

4-3 Definition of Macros for Accessing e_flag Parts . . . . . . . . . . . . . . . . . . . . . . . 4-3

4-4 Section Header Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3

4-5 Definition of Opcode IDs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5

4-6 Definition of Macros for Accessing Opcode Parts. . . . . . . . . . . . . . . . . . . . . . . 4-5

4-7 Relocation Entry Defined with Elf32_Rela . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6

4-8 Program Header . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-21

5-1 Single-Line Instruction Group . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-5

5-2 Multiple-Line Instruction Group (SC140) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-5

List of Examples

x SC100 Application Binary Interface

SC100 Application Binary Interface 1-1

Chapter 1

Introduction

The SC100 application binary interface (ABI) defines a set of standards intended to ensure interoperability

between conforming software components, such as, compilers, assemblers, linkers, debuggers, and

assembly language code. These standards cover run-time aspects as well as object formats to be used by

compatible tool chains from the StarCore Technology Center, Agere Systems, Motorola, and third party

tools developers.

A benefit of this standard definition is interoperability of conforming tools. This allows users to select the

best tool for each phase of the application development cycle, rather than being constrained to using an

entire tool chain. Another benefit is compatibility of conforming libraries. Programmers can build

compatible binary libraries and assembly code libraries, and be assured of their continued compatibility

over time.

1.1 Overview

This ABI addresses the following types of standards:

• Low level run-time binary interface standards

— Processor-specific binary interface (the instruction set and representation of fundamental data

types)

— Function calling conventions (how arguments are passed and results are returned, how registers

are assigned, and how the calling stack is organized)

• Source-level standards

— C language (preprocessor predefines, name mapping, and intrinsics)

— Assembler syntax and directives

• Object-file binary interface standards

— Header convention

— Section layout

— Relocation information format

— Debugging information format

• Library standards

— Compiler run-time libraries (integer routines and floating-point routines)

1-2 SC100 Application Binary Interface

Introduction

1.2 Conformance

Features defined in this ABI are mandatory unless specifically stated otherwise. Optional features, if

implemented, must conform to the ABI.

1.3 References

The following standards provide useful reference information:

• Tool Interface Standard (TIS) Executable and Linking Format (ELF) Specification, Version 1.1,

UNIX Systems Laboratories, Portable Formats Specification, 1995

• DWARF Debugging Information Format, Revision: Version 2.0.0, Industry Review Draft, UNIX

International, Program Languages SIG, July 27, 1993

• ANSI/IEEE Std 754-1985, IEEE standard for binary floating-point arithmetic data types

• ISO/IEC 9899:1999(E), International Standard - Programming Languages—C, 2nd Edition,

International Organization for Standardization, December 1, 1999

The following StarCore documents are included by reference into this ABI. With the exception of the

design specification listed below, these documents are available through the StarCore web site at

http://www.starcore-dsp.com.

• SC100 Assembly Language Tools User’s Manual (MNSC100ALT/D)

Describes the SC100 assembler syntax and directives listed in Chapter 5

of this ABI.

• SC110 DSP Core Reference Manual (MNSC110CORE/D)

Describes the SC110 core architecture and programming model, including the SC110 instruction set.

• SC140 DSP Core Reference Manual (MNSC140CORE/D)

Describes the SC140 core architecture and programming model, including the SC140 instruction set.

• Support in the Assembler and Simulator Required for Correct Reporting of SC100 Restrictions

(design specification)

Defines which instruction set programming rules must be validated by the assembler and simulator,

and specifies the identifier that must be included in the error or warning message that is generated

when a given rule is violated. This document is an internal design specification that is available to

third parties under a non-disclosure agreement with the StarCore Technology Center.

The SC100 generation of core architectures currently includes two cores: the StarCore SC110 and the

StarCore SC140. As future cores become available, their respective core reference manuals should also be

considered part of this ABI.

Revision History

SC100 Application Binary Interface 1-3

1.4 Revision History

This Rev. 2.0 of the ABI supersedes the previous edition, Rev. 1.8, dated 04/2000. Major changes from the

previous edition include:

Chapter 2,

“Low-Level Binary Interface.”

• Updated discussion of fundamental data types, aggregates, and bit fields, with little-endian and

big-endian differences noted.

• Added sections on stack unwinding, register saving and restoring functions, function call modes,

address modifier modes, saturation mode, and data addressing models.

• Removed the section, “Interrupt Handlers.”

• Updated the calling conventions with these notable changes:

— If the first argument is a

long long (where implemented), double, or long double, it is

passed in D0 and D1, as if it were first stored in an 8-byte aligned memory area and then the

low-addressed word were loaded into D0 and the high-addressed word into D1.

— Each argument on the stack is passed in the byte order appropriate for the endian mode.

— A function with a variable number of arguments passes the last fixed argument and all subsequent

variable arguments on the stack.

— An argument that is 8-byte aligned is passed 8-byte aligned on the stack. All other arguments are

passed 4-byte aligned on the stack.

— Arguments are passed on the stack, in order, from higher addresses to lower addresses. Each

argument on the stack is passed in the byte order appropriate for the endian mode.

— A

long long, double, or long double return value is returned in D0 and D1, as if it were first

stored in an 8-byte aligned memory area and then the low-addressed word were loaded into D0

and the high-addressed word into D1.

— A function returning a structure or union of any size receives in R2 the address of space in which

to return the structure or union. The function does not return that address in R2.

— The extension registers, D6.e and D7.e, are callee saved; the remaining extension registers are

caller saved.

— The MCTL register is caller saved.

— A compiler assumes the rounding mode default is two’s complement rounding, and the scaling

mode default is no scaling.

Chapter 3,

“High-Level Languages Issues.”

• Added new C preprocessor predefines:

__SC110__, __SC140__, __LITTLE_ENDIAN__, and

__BIG_ENDIAN__.

• Removed requirement for support of C in-line assembly syntax.

• Changed names of existing floating-point routines and integer routines, and added

double and long

long routines. Also added descriptions of all routines.

• Added new section on intrinsics for accessing architectural features.

Chapter 4,

“Object File Format.”

• Updated the list of SC100 ELF sections.

• Added sections on SC100 special sections and debugging information.

• Replaced the relocation section with a new relocation scheme.

1-4 SC100 Application Binary Interface

Introduction

Removed original Chapter 5, “Endian Support.” This revision of the ABI incorporates endian information

in individual sections, as appropriate, throughout the document.

Chapter 5,

“Assembler Syntax and Directives” (originally Chapter 6 in Rev 1.8).

• Removed requirement for support of object file control directives, in addition to the individual

directives MODE, DUPA, DUPC, DUPF, EXITM, MACLIB, MACRO, and PMACRO.

• Added requirement for support of ELSE and FALIGN directives.

• Added requirements for checking SC100 programming rules.

1.5 Acknowledgements

The SC100 Application Binary Interface team included representatives from the following companies:

We gratefully thank all participants for devoting their time and effort to create this standard.

Agere Systems Inc. Metrowerks, Inc.

Altium Limited Motorola, Inc.

Green Hills Software, Inc. WindRiver Systems, Inc.

Lineo, Inc.

SC100 Application Binary Interface 2-1

Chapter 2

Low-Level Binary Interface

This chapter defines low-level system standards for the SC100 generation of DSP cores, including:

• Processor-specific binary interface (the instruction set and representation of fundamental data types)

• Function calling conventions (how arguments are passed and results are returned, how registers are

assigned, and how the calling stack is organized)

2.1 Core Architecture

The SC100 generation of core architectures currently includes three cores: the StarCore SC110, the

StarCore SC140, and the StarCore SC140E. The architecture and instruction set for each core is defined in

that core’s respective reference manual, as listed in Section 1.3,

“References.” Programs written for these

cores use their instruction sets, as well as the instruction encodings and semantics of their architecture.

Programmers may assume that the instructions for these cores work as documented. Note that while an

ABI-conforming SC110 program will run on an ABI-conforming SC140 processor, the reverse is not

always true.

To conform to the ABI, the processor must execute the architecture’s instructions and produce the

expected results. This ABI does not define requirements for the services provided by an operating system,

nor does it specify what instructions must be implemented in hardware. A software emulation of the

architecture could conform to the ABI.

Programs that use non-SC100 instructions or capabilities do not conform to the SC100 ABI. Such

programs may produce unexpected results when run on machines lacking the non-SC100 capability.

2-2 SC100 Application Binary Interface

Low-Level Binary Interface

2.2 Endian Support

The SC100 architecture supports both big-endian and little-endian implementations. This standard defines

a binary interface for each. Note that program binaries that run on a big-endian implementation are not

portable to a little-endian implementation, and vice versa. The same applies to the data generated by these

programs, as well as to the layout of data used by these programs (such as the layout of data generated by

compilation tools).

The bytes that form the supported data types are ordered in memory according to the following:

• In a big-endian implementation, the most significant byte (MSB) is located in the lowest address

(byte 0).

• In a little-endian implementation, the least significant byte (LSB) is located in the lowest address

(byte 0).

2.3 Fundamental Data Types

The SC100 architecture defines the following data types:

• An 8-bit byte

• A 16-bit word

• A 32-bit long word

• A 64-bit double-long word

The following examples illustrate the bit and byte numbering for these data types.

Example 2-1. Word Bit and Byte Numbering

bit 15 8 7 0

byte 1

MSB LSB

byte 0

Little-Endian

bit 15 8 7 0

byte 0

MSB LSB

byte 1

Big-Endian

Fundamental Data Types

SC100 Application Binary Interface 2-3

Example 2-2. Long Word Bit and Byte Numbering

Example 2-3. Double-Long Word Bit and Byte Numbering

bit 31 24 23 16 15 8 7 0

byte 3

MSB LSB

byte 0

Little-Endian

bit 31 24 23 16 15 8 7 0

byte 0

MSB LSB

byte 3

Big-Endian

bit 31 24 23 16 15 8 7 0

Little-Endian

byte 3

LSB

byte 0

bit 63 56 55 48 47 40 39 32

byte 7

MSB

byte 4

bit 63 56 55 48 47 40 39 32

Big-Endian

byte 0

MSB

byte 3

bit 31 24 23 16 15 8 7 0

byte 4

LSB

byte 7

2-4 SC100 Application Binary Interface

Low-Level Binary Interface

Table 2-1 shows the mapping between these fundamental data types and the C language data types. Note

that fundamental data is always naturally aligned; that is, a double-long word is 8-byte aligned, a long

word is 4-byte aligned, and a word is 2-byte aligned.

Table 2-1. Mapping of C Data Types to SC100

Type C Type

Size

(bits)

Align

(bits)

Limits SC100

_Bool

1

Notes:

1. This data type is specified in the latest ISO C definition (ISO/IEC 9899:1999). Support of this data type is

optional. If used, this data type must be implemented with the size and alignment shown.

8 8 0 .. 1 signed byte

Character char

88-2

7

.. 2

7

−1 signed byte

signed char

unsigned char 880 .. 2

8

−1 unsigned byte

short

16 16 -2

15

.. 2

15

−1 signed word

signed short

unsigned short 16 16 0 .. 2

16

−1 unsigned word

Integral int

32 32 -2

31

.. 2

31

−1 signed long word

signed int

enum

long

signed long

unsigned int

32 32 0 .. 2

32

−1 unsigned long word

unsigned long

long long

1

64 64 -2

63

.. 2

63

−1 signed double-long word

signed long long

1

unsigned long long

1

64 64 0 .. 2

64

−1 unsigned double-long word

Pointer pointer to data

32 32 0 .. 2

32

−1 unsigned long word

pointer to function

Floating

2

Point

2. Floating point types conform to the IEEE 754 format.

float 32 32

-3.402e

38

.. -1.175e

-38

1.175e

-38

.. 3.402e

38

unsigned long word

double

64 64

-1.797e

308

.. -2.225e

-308

2.225e

-308

.. 1.797e

308

unsigned double-long word

long double

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